Plastic resins are one of the most convenient materials and have been used widely in daily life since the 20th century. In addition, as mass production of plastic resins is realized due to development of the petrochemical industry, demand therefor is rapidly increasing and use of plastic resins is expanded from applications for daily life to applications for industry.
General-purpose resins were initially used mainly in daily necessities such as household goods, engineering plastics are mainly used in applications for industry or manufacturing industry and, furthermore, super engineering plastics are used in specific fields, beyond satisfying required properties of materials for general industries and its market is continuously expanding.
As the automobile industry is focusing on more lightweight automobiles, demand for plastics is increasing in more various fields, and demand for polymer materials needed due to development of new technologies such as IT, semiconductors, electric vehicles, and the like is already growing in a variety of fields and is expected to be increasing more broadly in near future.
Recently, to address environmental problems due to generally used existing plastics, use of polyalkylene carbonates, which are aliphatic alkylene carbonates based on carbon dioxide generated as a byproduct gas, has drawn much attention.
Among these aliphatic alkylene carbonates, polypropylene carbonate (PPC) is prepared by polymerizing propylene oxide and carbon dioxide using a special catalyst. Currently, in the U.S., Novomer and Eastman Kodak are co-developing PPC as a packaging material with excellent oxygen-blocking properties, Japan's Sumitomo Chemical Co., Ltd is trying to enhance physical properties of PPC through complexation with other plastics and, in particular, Tianquan and the like in China are commercially producing PPC thanks to active support from the Chinese government. However, productivity of PPC is limited due to deficiency in manufacturing technology, in particular catalyst technology. In South Korea, SK Innovation Co. Ltd has succeeded in production of carbon dioxide-based polymers by developing a catalyst technology capable of minimizing the amount of a cyclic carbonate and generating high molecular weight and, currently, a total of 16 institutions including enterprises, laboratories, universities, and the like are participating in “business for practical applications of green technology using byproduct gases” organized by Ulsan Technopark and are progressing development of eco-friendly products using carbon dioxide-based polymers and commercialization thereof.
However, polyalkylene carbonates having a glass transition temperature Tg of about 38 to 40° C. are easily brittle at Tg or less and are not suitable for use in molded products due to soft and sticky properties thereof at Tg or higher, which makes use thereof as a plastic material difficult. Thus, efforts to use polyalkylene carbonates as a raw material of plastic products by improving impact strength characteristics and adhesiveness through mixing a polyalkylene carbonate with other materials and molding the mixture have continued. In particular, soft and sticky properties of polyalkylene carbonates at Tg or higher cause a phenomenon in which polyalkylene carbonate pellets are easily agglomerated as time elapses and thus the polyalkylene carbonate pellets are not fed into a molding machine when performing molding and have serious defects in distribution of the pellets. Thus, such properties need to be improved.
For example, Japanese Patent Application Laid-open No. 2007-119609 discloses a resin composition with enhanced tensile strength, elastic modulus of elongation and pyrolysis temperature by mixing polypropylene carbonate with calcium carbonate.
In addition, Chinese Patent Application Publication No. 1793237 discloses technology for enhancing glass transition temperature and mechanical characteristics, in particular tensile strength and impact strength by using a resin composition prepared by mixing polypropylene carbonate with layered silicate clay.
However, these resin compositions do not exhibit desired mechanical properties and therefore efforts to address such problems of polyalkylene carbonates through blending with polyolefin such as polyethylene (PE), polypropylene (PP), or the like, which is the most generally used, inexpensive, and has excellent processability among plastics, have been made.
However, it is impossible to blend polyolefin with polyalkylene carbonate due to a big difference between solubility parameters thereof. That is, there is no miscibility between the two resins.
In this regard, technologies for mixing between materials, which are not blended due to their different properties, have been developed according to respective base materials. For example, U.S. patent application Ser. Nos. 4,206,967 and 3,953,655 disclose use of a polymer prepared by copolymerizing or grafting a material selected from the group consisting of carboxylic acid, an anhydride, ester monomers, and the like onto a main chain or side chain of polyolefin or the like to mix a polar polymer such as ethylene vinyl alcohol (EVOH), nylon, or the like and polyolefin.
However, unlike existing base materials mixed with polyolefin, such as EVOH, nylon, and the like, when the polymer prepared by copolymerizing or grafting a material selected from the group consisting of carboxylic acid, an anhydride, ester monomers, and the like onto a main chain or side chain of polyolefin or the like is used to mix polyalkylene carbonate and polyolefin, a mixture of the two resins is unstable and thus miscibility therebetween is significantly deteriorated and it is therefore difficult to apply existing technologies to polyalkylene carbonates.
Thus, there is an urgent need to develop a polyalkylene carbonate-based molded product with enhanced mechanical characteristics and adhesiveness by increasing miscibility between polyalkylene carbonate, which is an eco-friendly material, and polyolefin such as polyethylene, polypropylene, or the like, which is a generally used plastic.